Startup

The startup.ts file is where you customize your application's startup behavior. Everything in this file is executed before the server starts, giving you control over the initialization process.

Use cases

Here are typical tasks you might handle in the startup.ts file:

• Establish database connections.

• Seed the database with initial or default data.

• Validate environment variables.

• Perform other initialization tasks like setting up third-party services.

  • Monitoring or telemetry services (e.g., Sentry, Datadog).
  • Project-specific setup like loading configurations from files or APIs

• Register global event listeners or middlewares.

By default, the startup.ts file handles environment variable validation and database connection initialization.

Example

Below is a realistic example of how a startup.ts file might look:

import { initialize } from '@extensions/sqlite';
import { validate } from '@workspace/validation';
import z from 'zod';

const env = z.object({
  ...(await import('@extensions/sqlite')).env,
  CONNECTION_STRING: z.string().url(),
  NODE_ENV: z.enum(['development', 'production']),
});

await validate(env, process.env);

await initialize()
  .then(() => {
    console.log('Database initialized');
  })
  .catch(error => {
    console.error(error);
    process.exit(1);
  });

• Validates required environment variables and provides detailed error messages if anything is missing or invalid.

• Establishes a connection to your database, readying it for queries.

• If something critical like environment variables or database connections fails, the process exits immediately, saving you time debugging downstream issues and This ensures predictable behavior.